1. Field of the Invention
The present invention generally concerns kinematic mechanical space, or three-dimensional, mechanisms for translating motion, particularly angular rotational motion, transpiring in a one plane into a corresponding motion in another, orthogonal, plane. In particular, the present invention concerns rotational motion translation mechanisms particulary for use in pendulous accelerometers and inclinometers, and the accelerometers and inclinometers so formed.
2. Description of the Relevant Art
Kinematic mechanical space, or three-dimensional, mechanisms for translating motion in three dimensions are known in the prior art. A planar antecedent to a certain particular one of these mechanisms is called a four link mechanism. This planar mechanism consists of a rotating driving, or input, crank connecting through a connecting rod to an oscillating rocker, all substantialy in a single plane. The conic, or spherical, three-dimensional form of this four link mechanism employs a rotating input crank connected by an arcuate connecting rod to an oscillating rocker. A modified form of this conic linkage may employ extended pin connections. Another prior art planar antecedent to a certain particular three-dimensional kinematic space mechanism is represented by the planar mechanism of a slider-crank. Within this planar mechanism a rotating, driving, input, crank connects through a connecting rod to a slider, all of the crank, rod, and slider being substantially in one plane. The three-dimensional form of this mechanism is a conic slider-crank.
These prior art kinematic space mechanisms are capable, when constructed with appropriately robust components, of transmitting significant torque and power. Transmission of high levels of torque and power is not a primary concern of the kinematic mechanism in accordance with the present invention. These prior art kinematic mechanisms use bearings, cranks, and connecting rods which are precision fabricated, and costly. The kinematic mechanism in accordance with the present invention may be formed entirely of bent or angled braising rod, welding rod, or simple wire. Bearings are only optionally employed, and are not employed in the preferred embodiment of the invention. Consequently, the kinematic mechanism in accordance with the present invention is very simple of construction, and inexpensive, relative to those prior art mechanisms which generally transmit much greater forces.
Similarly to the prior art kinematic mechanisms, the present invention will be seen to translate motion, particularly rotational motion, at a variably preselected, variably predetermined, transfer function. Within the prior art a realization of some particular transfer function required the custom fabrication of connecting linkages, gears, and the like. However, the physical realization of a predeterminated and preselected transfer function is of improved simplicity within the kinematic mechanism of the present invention, basically involving only the creation of a bent wire(s) of and at a particular contour.
Prior art kinematic mechanisms often exhibit considerable friction in their movements. These movements often involve robust components of considerable mass which are often reciprocating, and therefore consume considerable energy. In contrast, a mechanical coupling within the kinematic mechanism in accordance with the present invention will occur when two wires, which may be lubricated, slide by each other. Accordingly, friction is very low. This low friction proves useful in a preferred application of kinematic mechanism in accordance with the present invention within accelerometers and inclinometers.
The prior art regarding accelerometers and inclinometers is also of importance relative to the present invention. A pendulous accelerometer is a well known prior art mechanism in which a pendulous mass is suspended to pivot in one or more axis of freedom. The motion of the pendulous mass is subject to the gravitational, as well as to the acceleration, forces. Consequently, a pendulous accelerometer also serves as a inclinometer. The motion of the pendulous mass is detected, and used to generate a display which is indicative of inclination and acceleration. Normally the motion detection transpires along each of a plurality of orthogonal axis.
Four areas wherein the mechanical construction of prior art accelerometers and inclinometer may be compared, or contrasted, with the accelerometer and inclinometer in accordance with the present invention include (i) the mechanical suspension of a mass for motion; (ii) the detection of motion and/or inclination of the suspended mass; (iii) the display, including the mechanical display, of the detected motion and/or inclination; and (iv) the coupling of the detection into the display.
In the first area it is known in the prior art to suspend masses for pivoting in a plane like a pendulum. A similar suspension is employed in the accelerometer and inclinometer in accordance with the present invention. The suspension of masses within the accelerometer and inclinometer in accordance with the present invention will be found to be somewhat simplified, and consequently somewhat rudimentary, in comparison to certain high performance precision accelerometers and inclinometers of the prior art. Particularly in such high performance prior art accelerometers and inclinometers, it is of considerable importance that a pendulous mass should experience a low friction freedom of movement. One electrical scheme for detecting the position of the pendulous mass with minimal restriction or friction on its motional freedom is to emit a light beam from the radius end of the pendulous mass. This light beam travels through space and intercepts a spatially extended array of light detectors disposed oppositely to the light-emitting end of the pendulum. Thereby the position of the pendulum can be determined with no mechanical resistance. The pendulums within the accelerometer and inclinometer in accordance with the present invention do not enjoy a total absence of mechanical resistance to their pendulous movements, but they do enjoy remarkably low restriction or friction to such movements. This very low friction, or sticking, is aided by vibration of a vehicle within which the accelerometer and inclinometer containing the pendulums is intended to be installed, and by the use of lubricants. The lubricants add a small viscous damping to the pendulous movements which damping is useful in the application of the present invention. This viscous damping is common in fluid-filled inclinometer tubes but is uncommon in mechanical inclinometers and accelerometers. Within a particularly intended vehicular application of the accelerometer and inclinometer in accordance with the present invention it is of no great detriment that a pendulous mass should experience both a small frictional resistance and a viscous damping to its pivoting motion.
In the second area the accelerometer and inclinometer apparatus in accordance with the present invention will have the motion of its pendulous mass mechanically detected. In order to permit such mechanical detection the pendulous mass will be affixed firmly to a shaft along the axis about which it pivots, and will be required to overcome the inertia and frictional resistance of inducing rotation in this affixed shaft. Furthermore, still further components are mechanically linked to the pendulous mass. However, all of these components, although exhibiting inertia and although incurring friction in their movements, are extremely lightweight. The mechanically linked components produce insignificant inertial and frictional resistance to the pivoting of the pendulous mass within the intended application of the apparatus in accordance with the present invention. Accordingly, the second area is one wherein the construction of prior art pendulous accelerometers and inclinometers differs from the accelerometer and inclinometer apparatus in accordance with the present invention because such prior art accelerometers and inclinometers predominantly employ electrical, as opposed to mechanical, means for detecting motion of the pendulous mass in order that no friction or damping should be induced in such motion.
In the third area regarding the display, including the mechanical display, of detected motion, the accelerometer and inclinometer in accordance with the present invention will be seen to employ conventional mechanical pointers. These pointers are mechanically deflected relative to scales, thereby giving an analog visual indication of motion. In accelerometers and inclinometers of the multi-axis type this direct analog indicating is uncommon. Rather, motion indications are often electronic displays. The electronic displays indicate motion in both analog and digital forms. The reason that electronics indications of motion predominate over mechanical indications of motion probably has more to do with the fourth area --the mechanical coupling of detected motion into the display of such detection --then it does with avoidance of frictional losses, viscous damping, etc. which was of concern in the second area.
It is in the fourth area that the accelerometer and inclinometer in accordance with the present invention is considerably different from the prior art. The accelerometer and inclinometer in accordance with the present invention employs a particular mechanical kinematic space mechanism, which mechanism is also in accordance with the present invention. The coupling by this kinematic space mechanism into the display of such motion is entirely mechanical. Accordingly by this construction, the multi-axis accelerometer and inclinometer in accordance with the present invention is entirely mechanical. It has no necessary electrical components, yet is still highly accurate and readable in its intended applications.
Regarding the intended applications of the combination accelerometer and inclinometer in accordance with the present invention, one particular, preferred, application is for use on a land or sea vehicle, most particularly in an automobile. It is known in the prior art to measure both the lateral, or sideways, and the longitudinal, or forwards and backwards, acceleration produced by an automobile as a measurement of the performance of the automobile. Particularly, the maximum sustainable lateral acceleration in "G's" before positive control of the automobile is lost is a measurement of the cornering capability of the automobile. The measurement of longitudinal "G" force in one direction is indicative of the acceleration of the automobile, and in the opposite direction is indicative of the braking, or deceleration, of the automobile.
All these quantities are of considerable interest both to the technically-minded and to automobile enthusiasts. They are regularly included in automotive performance tests conducted by automotive magazines and the like. Accelerometers producing an electronic display of automotive lateral and longitudinal accelerational performance are currently in use by test laboratories. Automotive accelerometers are available as manufacturers' options, or as accessory add-ons, to high-performance sports cars. Some of the problems interfering with a more widespread use of accelerometers in vehicles, including automobiles, are the high cost and uncertain reliability of any electronics incorporated within these accelerometers. The entirely mechanical accelerometer in accordance with the present invention is of modest cost and highly reliable.
Further concerning intended applications of the combined accelerometer and inclinometer apparatus in accordance with the present invention, it is known to equip many kinds of vehicles from earthmoving equipments to agricultural implements to submarines with inclinometers in order to indicate the operating angles of the vehicle, and the proximity of the current angular spatial alignment of the vehicle to its design limits. Particularly for land vehicles it is useful that angular orientation of the vehicle should be indicated, and that an alarm should potentially be sounded, before the vehicle slides or tips over with attendant damage to the vehicle and hazard to its operator(s) and/or to bystanders.